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/*
* Adapted from jemalloc, to protect against buffer overflow vulnerabilities.
*
* Copyright (C) 2002-2017 Jason Evans <jasone@canonware.com>.
* All rights reserved.
* Copyright (C) 2007-2012 Mozilla Foundation. All rights reserved.
* Copyright (C) 2009-2017 Facebook, Inc. All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are met:
* 1. Redistributions of source code must retain the above copyright notice(s),
* this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright notice(s),
* this list of conditions and the following disclaimer in the documentation
* and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDER(S) ``AS IS'' AND ANY EXPRESS
* OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
* MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO
* EVENT SHALL THE COPYRIGHT HOLDER(S) BE LIABLE FOR ANY DIRECT, INDIRECT,
* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
* LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
* PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
* LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE
* OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
* ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
/** \file guardedalloc/intern/mallocn_inline.h
* \ingroup MEM
*/
#ifndef __MALLOCN_INLINE_H__
#define __MALLOCN_INLINE_H__
MEM_INLINE bool MEM_size_safe_multiply(size_t a, size_t b, size_t *result)
{
/* A size_t with its high-half bits all set to 1. */
const size_t high_bits = SIZE_MAX << (sizeof(size_t) * 8 / 2);
*result = a * b;
if (UNLIKELY(*result == 0)) {
return (a == 0 || b == 0);
}
/*
* We got a non-zero size, but we don't know if we overflowed to get
* there. To avoid having to do a divide, we'll be clever and note that
* if both A and B can be represented in N/2 bits, then their product
* can be represented in N bits (without the possibility of overflow).
*/
return ((high_bits & (a | b)) == 0 || (*result / b == a));
}
#endif /* __MALLOCN_INLINE_H__ */
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